THE NEBVOT'S SYSTEM
of the inferior frontal sulcus may be separate,! oi as the fronto-marginal sulcus of Wernicke iF-M.S.1*.
The anterior part of the insula •'*) is exposed. It is bounded by the superior limiting <S.L.S. and fronto* orbital sulci (F-O.S.V The latter is loi%\ and in rig. 51 it is seen to join the inferior frontal sulcus. In some brains these bounding sulci actually meet and u;ap out the insula.
The excavated inferior surfaces of the frontal !obes» have orbital sulci (O.S.), which vary in arrangement.
The Sylvian fissure fL.S.1 i* sometimes bitid posteriorly, and the posterior end of the parallel sulcus (P.S.) may not curve round it.
The intraparietal system iI-P.S.) consists of an inferior postcentral (I.Po.S.), horizontal and transverse occipital sulci, the latter being concurrent with the simian sulcus (S.S.I, which reaches very large proportions in the Chimpanzee, Above the true intraparietal complex there is a long sulcus, which is compensatory in nature (Co.S.) ; and the parieto-occipital sulcus (P-O.S.) cuts on to the outer surface of the cerebrum behind it.
The region behind the simian sulcus has few sulci. It has the U-shaped lateral occipital sulcus tL.O.S.'i, which embraces the posterior part of the calcarine fissure (Ca.S.).
On the mesial aspect of the hemisphere there is a considerable internal part of the simian sulcus lying parallel to the parieto-occipital sulcus, and the latter joins the long calcarine sulcus, whose posterior extremity is bifid (fig. 51,c). The whole or part of the terminal.